/**
 * @desc   现金额转大写
 * @param  {Number} n
 * @return {String}
 */
module.exports = (n) => {
  const fraction = ['角', '分'];
  const digit = ['零', '壹', '贰', '叁', '肆', '伍', '陆', '柒', '捌', '玖'];
  const unit = [['元', '万', '亿'], ['', '拾', '佰', '仟']];
  const head = n < 0 ? '欠' : '';

  n = Math.abs(n);

  let s = '';

  for (let i = 0; i < fraction.length; i += 1) {
    s += (digit[Math.floor(n * 10 * Math.pow(10, i)) % 10] + fraction[i]).replace(/零./, '');
  }

  s = s || '整';

  n = Math.floor(n);

  for (let i = 0; i < unit[0].length && n > 0; i += 1) {
    let p = '';

    for (let j = 0; j < unit[1].length && n > 0; j += 1) {
      p = digit[n % 10] + unit[1][j] + p;

      n = Math.floor(n / 10);
    }

    s = p.replace(/(零.)*零$/, '').replace(/^$/, '零') + unit[0][i] + s;
  }

  return (
    head
    + s
      .replace(/(零.)*零元/, '元')

      .replace(/(零.)+/g, '零')

      .replace(/^整$/, '零元整')
  );
};
